Why do substances with hydrogen bonding generally have higher melting and boiling points?

Substances with hydrogen bonding exhibit higher melting and boiling points primarily due to the strong intermolecular forces associated with hydrogen bonds. Hydrogen bonds occur when a hydrogen atom, covalently bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine), experiences an electrostatic attraction to another electronegative atom. This type of bonding is particularly strong compared to other types of dipole-dipole interactions or London dispersion forces.

When substances with hydrogen bonding are heated or when energy is added, a significant amount of energy is required to overcome these hydrogen bonds to change from a liquid to a gas (boiling) or from solid to liquid (melting). The presence of hydrogen bonds thus leads to higher boiling and melting points because the strong attractions between molecules must be disrupted for phase changes to occur.

In contrast, substances that lack such strong intermolecular forces, such as those that only exhibit weaker van der Waals forces or dipole-dipole interactions, will generally have lower melting and boiling points.